Re: [PATCH 0/2] x86: Speed up ioremap operations

From: Andrew Morton
Date: Wed Aug 27 2014 - 19:06:20 EST

On Wed, 27 Aug 2014 17:59:27 -0500 Mike Travis <travis@xxxxxxx> wrote:

> We have a large university system in the UK that is experiencing
> very long delays modprobing the driver for a specific I/O device.
> The delay is from 8-10 minutes per device and there are 31 devices
> in the system. This 4 to 5 hour delay in starting up those I/O
> devices is very much a burden on the customer.

That's nuts.

> There are two causes for requiring a restart/reload of the drivers.
> First is periodic preventive maintenance (PM) and the second is if
> any of the devices experience a fatal error. Both of these trigger
> this excessively long delay in bringing the system back up to full
> capability.
> The problem was tracked down to a very slow IOREMAP operation and
> the excessively long ioresource lookup to insure that the user is
> not attempting to ioremap RAM. These patches provide a speed up
> to that function.

With what result?
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